Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 8

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available Flat polymer loop thermosyphons
EN
The flat horizontal polymer loop thermosyphon with flexible transport lines is suggested and tested. The thermosyphon envelope consists of a polyamide composite with carbon based high thermal conductive micro-, nanofilaments and nanoparticles to increase its effective thermal conductivity up to 11 W/(m°C). Rectangular capillary mini grooves inside the evaporator and condenser of thermosyphon are used as a mean of heat transfer enhancement. The tested working fluid is R600. Thermosyphon evaporator and condenser are similar in design, have a long service life. In this paper three different methods (transient, quasi-stationary, and stationary) have been used to determine the thermophysical properties of polymer composites used as an envelope of thermosyphon, which make it possible to design a wide range of new heat transfer equipment. The results obtained contribute to establish the viability of using polymer thermosyphons for ground heat sinks (solar energy storage), gas-liquid heat exchanger applications involving seawater and other corrosive fluids, efficient cooling of superconductive magnets impregnated with epoxy/carbon composites to prevent wire movement, enhance stability, and diminish heat generation.
EN
Vapordynamic thermosyphon (VDT) is an efficient heat transfer device. The two-phase flow generation and dynamic interaction between the liquid slugs and vapor bubbles in the annular minichannel of the VDT condenser are the main features of such thermosyphon, which allowed to increase its thermodynamic efficiency. VDT can transfer heat in horizontal position over a long distance. The condenser is nearly isothermal with the length of tens of meters. The VDT evaporators may have different forms. Some practical applications of VDT are considered.
3
Content available remote Solid sorption cooler with composite sorbent bed and heat pipe thermal control
EN
Three adsorbers cooler was experimentally investigated. Ammonia was chosen as a working fluid. Two adsorbers (twins) were filled with the same complex compound (activated carbon fibre with MnCl2 microcrystals on the filament surface). The third low temperature adsorber had second complex compound (activated carbon fibre with BaCl2 microcrystals on the filament surface). The cycle of physical adsorption and chemical reactions in the sorbent bed of adsorber was followed with condensation/evaporation of ammonia inside the pores of the sorbent material. The specific feature of the third adsorber is the time of its cold generation. It is the sum of the liquid evaporation time and the time of desorption/regeneration of ammonia in the sorbent bed. This is a novelty of cooler design, which increases the heat and cold generation capacity and rate. The cooler thermal management is based on vapordynamic thermosyphons. The solar heat is the source of energy of cooler. The sink of the cold is the air flow.
EN
In the 21st century the way to increase the efficiency of new sources of energy is directly related with extended exploration of renewable energy. This modern tendency ensures the fuel economy needs to be realized with nature protection. The increasing of new power sources efficiency (cogeneration, trigeneration systems, fuel cells, photovoltaic systems) can be performed by application of solid sorption heat pumps, regrigerators, heat and cold accumulators, heat transformers, natural gas and hydrogen storage systems and efficient heat exchangers.
5
Content available remote Solid sorption heat pumps for tri-generation
EN
Solid sorption heat pumps and coolers have a good potential to be used in the air-conditioning, electronic thermal control and transport applications. Recent application is focused on a small-scale combined cold, heat and power system, which utilizes the motor waste heat for cold production (tri-generation system). The main feature of this device is the innovative adsorbent bed consisting of a heat pipe heat exchanger, in which the finned tubes are coated with an active carbon fiber "Busofit", saturated with different metal salts (salt on the fiber). Owing to the advantageous sorption properties of the complex compound and the good heat transfer quality of the heat pipe, an advanced sorption heat pump can be heated efficiently by the low temperature heat source. The heat pump has two sources of cold, namely the low temperature sorbent bed canister and the principal evaporator. The working fluid is ammonia. The experimental results show a specific power of 500-550 W/kg of adsorbent. The most favorable situation is the case, when two sources of cold are welcomed. The goal of this research program is an improvement of the heat pump system from simple case of two reactors with two different salts to complicated system with three reactors, evaporator/condenser and two branches of coolers, acting out of phase to produce heat and cold simultaneously.
6
Content available remote Vaporization heat transfer in porous wicks of evaporators
EN
The experimental investigation of two-phase heat transfer in porous cylindrical element of the evaporator typical for heat transfer enhancement and its cooling efficiency. Propane was chosen as working fluid. The data obtained for a flooded and partially flooded horizontal tube with a sintered capillary-porous coating are analyzed to compare with the data of heat transfer for the tube disposed between two vertical plates with side mini-gaps and inside the coaxial tube with low gap (near 2 mm).
EN
An experimental investigation of propane boiling heat transfer was done on single horizontal smooth tubes and tubes with porous coverings. Three modes of heat transfer were determined on evaporation surfaces with increasing heat flux: free convection, a transitional mode (the average vapor bubble population was negligible) and developed boiling. The existence of the region length depends on saturation pressure, the kind of evaporation surface, and the direction of heat flux change. On heat flux reduction, a strong heat-flux hysteresis phenomenon was observed: the picture regarding changes of heat transfer regimes the same, but boiling extended into the region which was occupied by free convection. In the wide range of saturation pressures and heat fluxes, the intensity of heat transfer on the samples with porous coatings is high than that on the smooth surface samples. The research carried out showed that an application of metal porous covering with electric arc gas-thermal spraying allows one to increase significantly (3-5 times as high in the region of low heat loads, q < 8 kW/m2, and 2.5-3 times in the region of high heat fluxes, q > 8 kW/m2) the heat transfer intensity for propane boiling on horizontal tubes.
EN
Modern thermal control systems for the electronic cooling are considering such as heat pipes and two-phase thermosyphons for low, middle and high power electronic elements. Thermally driven sold sorption system are discussed as an emergency cooling possibility for the future cooling of electronics.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.